Chip on film package with reinforcing sheet

ABSTRACT

A chip on film package includes a base film, a patterned circuit layer, a chip and a reinforcing sheet. The base film includes a first surface, a second surface opposite to the first surface and a mounting region located on the first surface. The patterned circuit layer is disposed on the first surface. The chip is mounted on the mounting region and electrically connected to the patterned circuit layer. The reinforcing sheet is disposed on the first surface and/or the second surface and exposes the chip, wherein a flexibility of the reinforcing sheet is substantially equal to or greater than a flexibility of the base film.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of U.S. provisionalapplication Ser. No. 62/551,755, filed on Aug. 29, 2017. The entirety ofthe above-mentioned patent application is hereby incorporated byreference herein and made a part of this specification.

BACKGROUND 1. Technical Field

The present disclosure generally relates to a chip package and amanufacturing method of the chip package, in particular, to a chip onfilm package and a manufacturing method of the chip on film package.

2. Description of Related Art

To expand the market area of display devices such as liquid crystaldisplays (LCDs), with promotion of low cost, large scale, and highperformance, more pixels have to be integrated in a small area. Thus, asa lead pitch of a driver integrated circuit (IC) which controls eachpixel becomes finer within the display device, various packaging methodshave been developed.

Packaging methods mainly used in a display device field include a tapecarrier packaging (TCP) method, a chip on glass (COG) packaging method,a chip on film (COF) packaging method, and the like. These methods arereferred to as wireless methods. To promote reduction in fabricationcost and improvement in yield due to a fine pitch, the share of COFtechnology in the packaging market has gradually increased since thelate 1990s.

Since COF technology uses a base film on which fine wiring patterns areformed, the distance and pitch between neighboring leads can beminimized, thus maximizing lead density. Further, this COF technologycan employ semiconductor chips with a large number of chip pads and finepitch or large-sized semiconductor chips. Therefore, the COF technologyusing the base film achieves high-integrated and multi-functionalsemiconductor device.

The COF package has an excellent bending force and a good flexibility,compared to the conventional chip package, is of high quality. However,as the demand for the IC packages of higher performances increases, theexternal terminals of such IC package are required not only to beincreased in number but also to be more fine pitch. As the level of thefine pitch of the external contacts of the IC package rises, naturallyit becomes necessary for the circuits on the base film of COF package tohave fine pitch contacts in order to electrically connect the externalterminals of the IC package. The thickness of the fine-pitch circuit isalso reduces accordingly, which makes the fine-pitch circuit morevulnerable and easier to break.

SUMMARY

Accordingly, the present disclosure is directed to a chip on filmpackage and a manufacturing method of the chip on film package withfavourable yield rate.

The present disclosure provides a chip on film package includes a basefilm, a patterned circuit layer, a chip and a reinforcing sheet. Thebase film includes a first surface, a second surface opposite to thefirst surface and a mounting region located on the first surface. Thepatterned circuit layer is disposed on the first surface. The chip ismounted on the mounting region and electrically connected to thepatterned circuit layer. The reinforcing sheet is disposed on the firstsurface and/or the second surface and exposes the chip, wherein aflexibility of the reinforcing sheet is substantially equal to orgreater than a flexibility of the base film.

According to an embodiment of the present disclosure, the reinforcingsheet is disposed on the first surface and includes a first openingexposing the chip.

According to an embodiment of the present disclosure, the reinforcingsheet directly disposed on the patterned circuit layer and the firstopening exposes a part of the patterned circuit layer where the chip ismounted.

According to an embodiment of the present disclosure, the chip on filmpackage further includes a solder resist layer disposed on the patternedcircuit layer and including a second opening exposing a part of thepatterned circuit layer where the chip is mounted, the reinforcing sheetis disposed on the solder resist layer and exposes the second opening.

According to an embodiment of the present disclosure, a size of thereinforcing sheet is substantially smaller than a size of the solderresist layer, and a gap maintains between an outer edge of thereinforcing sheet and an outer edge of the solder resist layer.

According to an embodiment of the present disclosure, the chip on filmpackage further includes an underfill disposed between the chip and thebase film and covering the patterned circuit layer exposed by the firstopening.

According to an embodiment of the present disclosure, the reinforcingsheet is disposed on the second surface.

According to an embodiment of the present disclosure, the reinforcingsheet includes a plurality of chamfered corners.

According to an embodiment of the present disclosure, the chip on filmpackage further includes an adhesive layer disposed between thereinforcing sheet and the base film.

According to an embodiment of the present disclosure, the patternedcircuit layer includes a plurality of circuit lines and a fine-pitchregion, and the reinforcing sheet covers the circuit lines in thefine-pitch region.

According to an embodiment of the present disclosure, a pitch betweenadjacent two of the circuit lines in the fine-pitch region issubstantially smaller than 20 μm, and a width of each of the circuitlines ranges from 5 μm to 11 μm.

According to an embodiment of the present disclosure, a material of thereinforcing sheet includes polyimide (PI).

According to an embodiment of the present disclosure, a thickness of thereinforcing sheet ranges from 3 μm to 40 μm.

The present disclosure provides a manufacturing method of a chip on filmpackage. The method includes the following steps. A base film isprovided, wherein the base film includes a first surface, a secondsurface opposite to the first surface and a mounting region located onthe first surface. A patterned circuit layer is formed on the firstsurface. A chip is mounted on the mounting region, wherein the chip iselectrically connected to the patterned circuit layer. A reinforcingsheet is laminated onto the first surface and/or the second surface,wherein a flexibility of the reinforcing sheet is substantially equal toor greater than a flexibility of the base film.

According to an embodiment of the present disclosure, the reinforcingsheet is laminated onto the first surface and/or the second surfacebefore the chip is mounted on the mounting region, and the reinforcingsheet covers patterned circuit layer and exposing the mounting region.

According to an embodiment of the present disclosure, the reinforcingsheet is laminated onto the second surface after the chip is mounted onthe mounting region.

According to an embodiment of the present disclosure, the reinforcingsheet is laminated onto the first surface and/or the second surface by alaminating roller configured to roll over the first surface and/or thesecond surface.

According to an embodiment of the present disclosure, the step oflaminating the reinforcing sheet onto the first surface and/or thesecond surface further includes a heating process.

According to an embodiment of the present disclosure, a heatingtemperature of the heating process ranges from 80° C. to 170° C., and aheating period of the heating process ranges from 1 minute to 60minutes.

According to an embodiment of the present disclosure, the manufacturingmethod of the chip on film package further includes the following steps.An adhesive layer is formed on the first surface and/or the secondsurface before the reinforcing sheet is laminated onto the first surfaceand/or the second surface.

In light of the foregoing, in the chip on film package of thedisclosure, the reinforcing sheet is disposed on the first surfaceand/or the second surface of the base film and exposes the chip on thebase film. Moreover, the flexibility of the reinforcing sheet issubstantially equal to or greater than the flexibility of the base filmto provide flexibility and protection to the patterned circuit layer onthe base film, so as to avoid fracture of fine circuit lines of thepatterned circuit layer. Therefore, yield rate of the chip on filmpackage is significantly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate embodiments of thedisclosure and, together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 illustrates a cross-sectional view of a chip on film packageaccording to an embodiment of the disclosure.

FIG. 2 illustrates a top view of a chip on film package according to anembodiment of the disclosure.

FIG. 2A illustrates a top view of a part of components of a chip on filmpackage according to an embodiment of the disclosure.

FIG. 3 illustrates a cross-sectional view of a chip on film packageaccording to an embodiment of the disclosure.

FIG. 4 illustrates a cross-sectional view of a chip on film packageaccording to an embodiment of the disclosure.

FIG. 5 and FIG. 6 illustrate a part of a manufacturing process of a chipon film packages according to embodiments of the disclosure.

FIG. 7 and FIG. 8 illustrate a part of a manufacturing process of a chipon film packages according to embodiments of the disclosure.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1 illustrates a cross-sectional view of a chip on film packageaccording to an embodiment of the disclosure. FIG. 2 illustrates a topview of a chip on film package according to an embodiment of thedisclosure. Referring to FIG. 1 and FIG. 2, in some embodiments, thechip on film package 100 may include a base film 110, a patternedcircuit layer 120, a chip 130 and a reinforcing sheet 140. The base film110 includes a first surface 112, a second surface 114 opposite to thefirst surface and a mounting region R1 located on the first surface 112.In some embodiments, the base film 110 may include an insulatingmaterial such as, but not limited to, polyimide (PI). The patternedcircuit layer 120 is disposed on the first surface 112. In someembodiments, the patterned circuit layer 120 is formed on the firstsurface 112 of the base film 110 by, for example, electroplating andetching processes, etc. The chip 130 may be mounted on the mountingregion R1 by surface mount technology (SMT) and electrically connectedto the patterned circuit layer 120. In some embodiments, the patternedcircuit layer 120 may include a plurality of pads on which the chip 130is mounted.

In some embodiments, the reinforcing sheet 140 is disposed on the firstsurface 112 and/or the second surface 114 and exposes the chip 130. Insome embodiments, the reinforcing sheet 140 may be a flexible sheet andthe flexibility of the reinforcing sheet 140 is substantially equal toor greater than the flexibility of the base film 110. In someembodiments, the material of the reinforcing sheet 140 may include PI,which includes a condensation product of an acid anhydride, a diaminecompound, etc. The reinforcing sheet 140 may be laminated onto the firstsurface 112 and/or the second surface 114 of the base film by alaminating roller (e.g. the laminating roller 200 shown in FIG. 5 andFIG. 8). The thickness of the reinforcing sheet 140 may range from 3 μmto 40 μm. With such arrangement, the reinforcing sheet 140 is configuredto provide flexibility and protection to the patterned circuit layer120, so as to avoid fracture of fine circuit lines of the patternedcircuit layer 120.

In one of the implementations, the reinforcing sheet 140 is disposed onthe first surface 112 as shown in FIG. 1. The reinforcing sheet 140 mayinclude a first opening 142 exposing the mounting region R1 and the chip130 disposed on the mounting region R1. In some embodiments, the chip onfilm package 100 may further include a solder resist layer 150, which isdisposed on the patterned circuit layer 120. The solder resist layer 150may include a second opening 152 exposing a part of the patternedcircuit layer 120 where the chip 130 is mounted. In such embodiments,the reinforcing sheet 140 is disposed on the solder resist layer 150 andthe first opening 142 exposes the second opening 152 and a part of thesolder resist layer 150 surround the second opening 152 as shown in FIG.1.

In addition, the size of the reinforcing sheet 140 is substantiallysmaller than the size of the solder resist layer 150, and a gap G1maintains between an outer edge of the reinforcing sheet 140 and anouter edge of the solder resist layer 150. In some embodiments, the chipon film package 100 may be formed by Reel to Reel production, so aplurality of chip on film packages 100 in a roll are singularized bypunch process. In some embodiments, the reinforcing sheet 140 may bedisposed within a punch lines of the chip on film package 100.Accordingly, when the chip on film package 100 is punched to besingularized, a gap may exist between the outer edge of the reinforcingsheet 140 and the outer edge (i.e. the punch line) of the chip on filmpackage 100. As such, the issue of the reinforcing sheet 140 peelingfrom the base film 110 can be reduced. Moreover, the reinforcing sheet140 may further include a plurality of chamfered corners 144 as shown inFIG. 2 to further improve peeling issues of the reinforcing sheet 140.

In some embodiments, the chip on film package 100 further includes anunderfill 160, which is disposed between the chip 130 and the base film110 and covers the patterned circuit layer 120 exposed by the firstopening 142. In some embodiments, the underfill 160 may be furtherfilled between a side surface of the chip 130 and a side surface of thesolder resist layer 150 exposed by the first opening 142 of thereinforcing sheet 140 as shown in FIG. 1. In the present embodiment, agap exist between the side surface of the first opening 142 and the sidesurface of the chip 130. For example, the gap G2 may exist between theside surface of the first opening 142 and a short side surface of thechip 130, and the gap G3 may exist between another side surface of thefirst opening 142 and a long side surface of the chip 130 as shown inFIG. 2. Preferably but not limitedly, the width of the gap G2 may besubstantially the same as the width of the gap G3. Alternatively, thewidth of the gap G2 may be different from the width of the gap G3.

In some embodiments, the chip on film package 100 may further include anadhesive layer 170, which is disposed between the reinforcing sheet 140and the base film 110, such that the reinforcing sheet 140 is laminatedand attached to the base film 110 via the adhesive layer 170. In someembodiments, the adhesive layer 170 may be omitted, and the reinforcingsheet 140 is laminated onto the base film 110 merely by applyingpressure thereon. In some embodiments, the reinforcing sheet 140 islaminated onto the base film 110 by applying both heat and pressurethereon. Namely, the method of laminating the reinforcing sheet 140 ontothe first surface 112 and/or the second surface 114 may further includea heating process. For example, the heating temperature of the heatingprocess may range from 80° C. to 170° C., and the heating period of theheating process may range from 1 minute to 60 minutes. The presentembodiment is merely for illustration, and the disclosure is not limitedthereto.

FIG. 2A illustrates a top view of a part of components of a chip on filmpackage according to an embodiment of the disclosure. It is noted that,for the sake of clarity and simplicity, the reinforcing sheet 140 andthe solder resist layer 150 are omitted in FIG. 2A to better illustratethe layout of the patterned circuit layer 120. Referring to FIG. 1 andFIG. 2A, in some embodiments, the patterned circuit layer 120 mayinclude a plurality of circuit lines 122 and a fine-pitch region R2. Thefine-pitch region R2 has a first portion and a second portion, and thefirst portion is disposed closer to the chip 130 than the secondportion. In the fine-pitch region R2, the density of the circuit lines122 is high, so that a pitch P1 between adjacent two of the circuitlines 122 may be extremely fine. Accordingly, the width and thethickness of each circuit line 122 is also limited. For example, a pitchP1 between adjacent two of the circuit lines 122 in the first portionmay be substantially smaller than 20 μm, a thickness of each of thecircuit lines 122 may be less than 8 μm, a width of each of the circuitlines 122 may range from 5 μm to 11 μm, and the pitch in the secondportion may be substantially greater than the pitch in the firstportion. Therefore, the circuit lines 122 in the fine-pitch region R2would be easily fractured due to lacking of mechanical strength. In suchembodiments, the reinforcing sheet 140 at least covers the circuit lines122 in the fine-pitch region R2 so as to protect the circuit lines 122underneath and also provide flexibility to the circuit lines 122 and thebase film 110. Accordingly, when the chip on film package 100 suffersimpact or bending, the fracture of the circuit lines 122 in thefine-pitch region R2 can be significantly improved, so as to increasethe yield rate of the chip on film package 100. In other embodiments,for similar purposes, the reinforcing sheet 140 may also covers the partof the base film 110 where circuit lines 122 turns in direction (e.g.the circled region in FIG. 2A).

FIG. 3 illustrates a cross-sectional view of a chip on film packageaccording to an embodiment of the disclosure. It is noted that the chipon film package 100 a shown in FIG. 3 contains many features same as orsimilar to the chip on film package 100 disclosed earlier with FIG. 1 toFIG. 2A. For purpose of clarity and simplicity, detail description ofsame or similar features may be omitted, and the same or similarreference numbers denote the same or like components. The maindifferences between the chip on film package 100 a shown in FIG. 3 andthe chip on film package 100 shown in FIG. 1 are described as follows.

Referring to FIG. 3, in some embodiments, the reinforcing sheet 140 isdisposed on the second surface 114 of the base film 110. In the presentembodiments, the reinforcing sheet 140 is laminated and attached to thebase film 110 via the adhesive layer 170. In some embodiments, theadhesive layer 170 may be omitted, and the reinforcing sheet 140 islaminated onto the base film 110 merely by applying pressure thereon. Insome embodiments, the method of laminating the reinforcing sheet 140onto the second surface 114 may further include a heating process. Forexample, the heating temperature of the heating process may range from80° C. to 170° C., and the heating period of the heating process mayrange from 1 minute to 60 minutes.

In some embodiments, the reinforcing sheet 140 may be disposed on theentire second surface 114 of the base film 110. In other embodiments, agap may exist between the outer edge of the reinforcing sheet 140 andthe outer edge (i.e. the punch line) of the chip on film package 100, soas to reduce the issue of the reinforcing sheet 140 peeling from thebase film 110. Moreover, the reinforcing sheet 140 may further include aplurality of chamfered corners (similar to the chamfered corners 144shown in FIG. 2) to further improve peeling issues of the reinforcingsheet 140. Alternatively, the reinforcing sheet 140 may be disposed onthe region of the second surface 114 corresponding to the fine-pitchregion R2 of the first surface 112, so as to provide flexibility to thecircuit lines 122 and the base film 110. For example, the reinforcingsheet 140 may be disposed on the region of the second surface 114 rightbeneath the fine-pitch region R2 of the first surface 112. In otherembodiments, the reinforcing sheet 140 may also be disposed on theregion of the second surface 114 right beneath the circled region inFIG. 2A.

FIG. 4 illustrates a cross-sectional view of a chip on film packageaccording to an embodiment of the disclosure. It is noted that the chipon film package 100 b shown in FIG. 4 contains many features same as orsimilar to the chip on film packages 100, 100 a disclosed earlier withFIG. 1 to FIG. 3. For purpose of clarity and simplicity, detaildescription of same or similar features may be omitted, and the same orsimilar reference numbers denote the same or like components. The maindifferences between the chip on film package 100 b shown in FIG. 4 andthe chip on film packages 100, 100 a shown in FIG. 1 to FIG. 3 aredescribed as follows.

Referring to FIG. 4, in some embodiments, the reinforcing sheet 140 mayinclude a first reinforcing sheet 140 a disposed on the first surface112 and a second reinforcing sheet 140 b disposed on the second surface114. The first reinforcing sheet 140 a is directly disposed on thepatterned circuit layer 120 and the first opening 142 exposes a part ofthe patterned circuit layer 120 where the chip 130 is mounted. Namely,in the present embodiments, the solder resist layer 150 is omitted andis replaced by the reinforcing sheet 140. The adhesive layer 170 is alsoomitted herein. Similarly, the second reinforcing sheet 140 b isdirectly disposed on the second surface 114 without the help of theadhesive layer 170. In the present embodiment, the reinforcing sheets140 a, 140 b are laminated onto the base film 110 merely by applyingpressure thereon. In addition, the step of laminating the reinforcingsheets 140 a, 140 b onto the first surface 112 and the second surface114 may further include a heating process. For example, the heatingtemperature of the heating process may range from, but not limited to,80° C. to 170° C., and the heating period of the heating process mayrange from, but not limited to, 1 minute to 60 minutes.

FIG. 5 and FIG. 6 illustrate a part of a manufacturing process of a chipon film packages according to embodiments of the disclosure. Referringto FIG. 1, FIG. 5 and FIG. 6, in some embodiments, the reinforcing sheet140 may be laminated onto the first surface 112 and/or the secondsurface 114 before the chip is mounted on the mounting region R1. It isnoted that the reinforcing sheet 140 being laminated onto the firstsurface 112 is depicted in FIG. 5 for illustration purpose, but thedisclosure is not limited thereto. In other embodiments, the reinforcingsheet 140 may also be laminated onto the second surface 114.Accordingly, in the manufacturing process of the chip on film package100/100 a/100 b, the base film 110 is firstly provided, and thepatterned circuit layer 120 is then formed on the first surface 112 ofthe base film 110. In some embodiments, the solder resist layer 150 canbe optionally formed on the patterned circuit layer 120. Next, thereinforcing sheet 140 is laminated onto the first surface 112 and/or thesecond surface 114 of the base film 110, and the chip 130 is thenmounted on the mounting region R1 of the base film 110 to beelectrically connected to the patterned circuit layer 120.

Referring to FIG. 5, in some embodiments, the reinforcing sheet 140 mayinclude one or more first openings 142 (multiple first openings 142 areillustrated herein) corresponding to the mounting regions R1 of the basefilm 110. Then, the reinforcing sheet 140 including the first openings142 is laminated onto the first surface 112 (and/or the second surface114) by a laminating roller 200, which is configured to roll over thereinforcing sheet 140 on the first surface 112 and/or the second surface114 to apply pressure evenly on the reinforcing sheet 140. For theembodiments of the reinforcing sheets 140 a, 140 b being laminated ontoboth the first surface 112 and the second surface 114, two laminatingrollers 200 may be applied to both sides of the base film respectivelyto laminate the reinforcing sheets 140 a, 140 b onto the first surface112 and the second surface 114 at the same time. In some embodiments, anadhesive layer (e.g. the adhesive layer 170 as shown in FIG. 1 and FIG.3) may be formed on the first surface 112 and/or the second surface 114before the reinforcing sheet 140 is laminated, but the disclosure is notlimited thereto.

Then, referring to FIG. 6, one or more chips 130 (multiple chips 130 areillustrated herein) are disposed in the first openings 142 respectivelyto be mounted on the mounting regions R1 of the base film 110, and thechips 130 are electrically connected to the patterned circuit layer 120.Then, the resulting structure is punched to be singularized and form aplurality of chip on film packages 100/100 a/100 b as shown in FIG. 1,FIG. 3 or FIG. 4.

FIG. 7 and FIG. 8 illustrate a part of a manufacturing process of a chipon film packages according to embodiments of the disclosure. Referringto FIG. 3, FIG. 7 and FIG. 8, in the embodiments of the reinforcingsheet 140 being laminated onto the second surface 114, the reinforcingsheet 140 may be laminated onto the second surface 114 after the chip ismounted on the mounting region R1. Accordingly, in the manufacturingprocess of the chip on film package 100 a, the base film 110 is firstlyprovided, and the patterned circuit layer 120 is then formed on thefirst surface 112 of the base film 110. In some embodiments, the solderresist layer 150 can be optionally forming on the patterned circuitlayer 120. Next, the chip 130 is mounted on the mounting region R1 ofthe base film 110 to be electrically connected to the patterned circuitlayer 120, and the reinforcing sheet 140 is then laminated onto thesecond surface 114 of the base film 110.

Referring to FIG. 7, in some embodiments, one or more chips 130(multiple chips 130 are illustrated herein) are mounted on the mountingregions R1 of the base film 110 are electrically connected to thepatterned circuit layer 120. Then, the reinforcing sheet 140 islaminated onto the second surface 114 by the laminating roller 200,which is configured to roll over the reinforcing sheet 140 on the secondsurface 114 to apply pressure evenly on the reinforcing sheet 140. Insome embodiments, an adhesive layer (e.g. the adhesive layer 170 asshown in FIG. 1 and FIG. 3) may be formed on the second surface 114before the reinforcing sheet 140 is laminated, but the disclosure is notlimited thereto. Then, the resulting structure is punched to besingularized and form a plurality of chip on film packages 100 a asshown in FIG. 3.

In sum, in the chip on film package of the disclosure, the reinforcingsheet is disposed on the first surface and/or the second surface of thebase film and exposes the chip on the base film. The flexibility of thereinforcing sheet is substantially equal to or greater than theflexibility of the base film to provide flexibility and protection tothe patterned circuit layer on the base film, so as to avoid fracture offine circuit lines of the patterned circuit layer. In addition, thereinforcing sheet may be disposed at least on the region of the basefilm corresponding to the fine-pitch region of the patterned circuitlayer to provide flexibility to the patterned circuit layer and the basefilm. Accordingly, when the chip on film package suffers impact orbending, the fracture of the patterned circuit layer in the fine-pitchregion can be avoided. Therefore, yield rate of the chip on film packageis significantly improved.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentdisclosure without departing from the scope or spirit of the disclosure.In view of the foregoing, it is intended that the present disclosurecover modifications and variations of this disclosure provided they fallwithin the scope of the following claims and their equivalents.

What is claimed is:
 1. A chip on film package, comprising: a base filmcomprising a first surface, a second surface opposite to the firstsurface and a mounting region located on the first surface; a patternedcircuit layer disposed on the first surface; a chip mounted on themounting region and electrically connected to the patterned circuitlayer; and a reinforcing sheet disposed on the first surface and/or thesecond surface and exposing the chip, wherein a flexibility of thereinforcing sheet is substantially greater than a flexibility of thebase film, wherein the patterned circuit layer comprises a plurality ofcircuit lines and a fine-pitch region, and the reinforcing sheet coversthe circuit lines in the fine-pitch region, wherein the fine-pitchregion has a first portion and a second portion, and the first portionis disposed closer to the chip than the second portion, wherein everyadjacent two of the circuit lines has a pitch therebetween, only thepitch in the first portion is substantially smaller than 20 μm, and awidth of each of the circuit lines ranges from 5 μm to 11 μm, whereinthe pitch in the second portion is substantially greater than the pitchin the first portion.
 2. The chip on film package according to claim 1,wherein the reinforcing sheet is disposed on the first surface andcomprises a first opening exposing the chip.
 3. The chip on film packageaccording to claim 2, wherein the reinforcing sheet is directly disposedon the patterned circuit layer and the first opening exposes a part ofthe patterned circuit layer where the chip is mounted.
 4. The chip onfilm package according to claim 2, further comprising a solder resistlayer disposed on the patterned circuit layer and comprising a secondopening exposing a part of the patterned circuit layer where the chip ismounted, the reinforcing sheet is disposed on the solder resist layerand exposes the second opening.
 5. The chip on film package according toclaim 4, wherein a size of the reinforcing sheet is substantiallysmaller than a size of the solder resist layer, and a gap maintainsbetween an outer edge of the reinforcing sheet and an outer edge of thesolder resist layer.
 6. The chip on film package according to claim 2,further comprising an underfill disposed between the chip and the basefilm and covering the patterned circuit layer exposed by the firstopening.
 7. The chip on film package according to claim 1, wherein thereinforcing sheet is disposed on the second surface.
 8. The chip on filmpackage according to claim 1, wherein the reinforcing sheet comprises aplurality of chamfered corners.
 9. The chip on film package according toclaim 1, further comprising an adhesive layer disposed between thereinforcing sheet and the base film.
 10. The chip on film packageaccording to claim 1, wherein a material of the reinforcing sheetcomprises polyimide (PI).
 11. The chip on film package according toclaim 1, wherein a thickness of the reinforcing sheet ranges from 3 μmto 40 μm.